Abstract
Ketamine is an N-methyl-D-aspartate receptor antagonist widely used as an anesthetic. The subanesthetic dose of ketamine has been reported to have an analgesic effect. Since ketamine is currently not commercially available except in an injectable form in Japan, several pharmaceutical preparations of ketamine for oral administration have been proposed for hospital use. Previously, we described a new pharmaceutical preparation of ketamine using agar, ketamine Agar-Gel. In the present study, we examined the analgesic effect and plasma concentration profiles of ketamine Agar-Gel when buccally administrated to a patient with postherpetic neuralgia. Pain intensity was measured using a numerical rating scale (NRS). Furthermore, we determined the plasma concentrations of ketamine and norketamine after administration of ketamine Agar-Gel. When ketamine Agar-Gel was administered, the pain intensity was reduced to 33-86% of the previous level and the effect lasted 3-4 hours. Two months after administration of the preparation, the pain resolved and no further treatment was required. The plasma concentration profile of ketamine and norketamine after buccal administration of ketamine differed from that after oral administration of ketamine reported previously, while the plasma concentrations of norketamine were almost the same as those of ketamine. We will examine the usefulness of ketamine Agar-Gel in additional cases.
